Wood flooring systems are available in a variety of types and size. Methods of installation of these various wood flooring systems vary greatly, with some requiring complicated and slow nailing or gluing techniques in order to lay and connect adjacent floorboards. One common type of wood flooring system has an interlocking joint commonly called a tongue-and-groove system. Many of these tongue-and-groove flooring systems work well. But to properly install most tongue-and-groove floors, it's often necessary to hire a contractor or other professional, which increases the total cost for the consumer and can delay the installation. It is generally preferred that flooring installations be simple enough to be done by the consumer without hiring a professional installer. Some tongue-and-groove wood flooring systems can be installed “floated,” meaning that their installation does not required complicated nailing or gluing, so that they can be easily installed by consumers without hiring professional installers. Floated installation is possible due to the design of the tongue-and-groove interlocking joint system. Interlocking tongue-and-groove joint systems that enable floated installations of wood flooring are commonly called “click systems.”
It is generally understood that “click system” refers to an interlocking joint system including two tongues and two grooves formed on four sides (edges) of a floorboard. And it's generally the case that floorboard long-side (longitudinal side) interlocking tongues/grooves and floorboard cross-side (butt-end side) interlocking tongues/grooves may have different shapes. Conventional click systems are designed to lock adjacent floorboards in position horizontally and vertically to prevent the adjacent floorboards from separating from each other horizontally and/or vertically after installation without any glue or nails. In addition, conventional click systems can be easily unlocked, which enables the user to uninstall the flooring and then reinstall it at different location. Conventional click systems have various forms/types including but not limited to snap-lock systems, rotatable-lock systems, drop-lock systems, etc., any of which typically can be provided with or without separate locking elements.
FIGS. 1-3 show one common prior-art solid-wood floorboard 10 with a click-type interlocking joint system 12. The floorboard 10 includes two tongues and two grooves formed on its four sides. A longitudinal-side tongue 14 is formed along one longitudinal side of the floorboard 10 and a longitudinal-side groove 16 is formed along the opposite longitudinal side of the floorboard, with the longitudinal-side tongue and groove sized and shaped to receive the longitudinal-side groove and tongue, respectively, of adjacently installed floorboards. And a butt-side tongue 18 is formed along one butt-end side of the floorboard 10 and a butt-side groove 20 is formed along the opposite butt-end side of the floorboard, with the butt-side tongue and groove sized and shaped to receive the butt-side groove and tongue, respectively, of adjacently installed floorboards.
Click systems are commonly used for laminate and engineered-wood flooring systems. Engineered flooring is typically made of a top layer and a core (or substrate). The top layer is typically a hardwood veneer and the core is typically plywood made of a softwood species such as but not limited to pine, spruce, poplar, birch, eucalyptus, etc. The core is typically made of several layers with crossed-direction fibers arranged to increase the stability of the floorboard.
Click systems are rarely used for solid-wood flooring. In solid-wood flooring systems, each individual floorboard is made of only one piece of wood, of a top layer and a butcher-block construction base, or of only a butcher-block construction. Click systems are rarely used for solid-wood flooring because after installation they are typically not stable enough and so the floor makes noises and squeaks when it's walked on. Squeaking is caused by two contacting wood surfaces sliding against each other, with the friction of the surfaces creating the noise. In general, surfaces with relatively low coefficients-of-friction can slide against each other more easily and not create noise. When a person walks on a solid-wood floor, the floorboards move up and down slightly when stepped on. The slight vertical movement of the floorboards creates friction at the point of contact between floorboards, and when this friction is too great it will create a squeaking noise.
Solid wood floorings are generally not stable enough to avoid squeaking because they're easily affected by variations in climate, especially the room air humidity and temperature. Wood is a hygroscopic material, meaning that wood material naturally interacts with the surrounding climate. If the climate is dry, then the wood material will tend to dry and in consequence to shrink. And if the climate is wet, then the wood material will tend to be absorb moisture and in consequence to expand. The consequences of this shrinking and/or expanding are a distortion (e.g., cupping, bending, and/or springing) of the shape and size of the floorboards and the interlocking joint system interconnecting them.
For solid-wood floorboards with a click system, this expansion and shrinkage make the floorboards difficult if not almost impossible to install such that they do not squeak. Plus, the resulting gaps or spaces between installed floorboards are a visual/aesthetic detraction. Such expansion and shrinkage is not such an issue for engineered or laminate flooring systems, as the fibers of the core are cross-directed, so the floorboard and the interlocking joint system are only negligibly at most affected by these climate variations.
Shrinking and expansion are generally proportional to the width and thickness of the floorboards. Wide floorboards generally experience more distortion than narrow floorboards. This tends to limit the width of solid-wood flooring to narrow sizes, generally less than about 90mm wide. Thick floorboards generally experience less distortion than thin floorboards. A known solution to increase the stability of solid-wood floorboards is to increase their thickness, but this added material significantly increases the cost of the flooring system.
Accordingly, a disadvantage of solid-wood flooring systems with click systems is that they are subject to shrinkage and/or expansion that causes distortion of the floorboards sufficient to result in squeaking when walking on the floor. Such squeaking can be so severe that it can lead some users to completely replace the floor, which is very expensive to do. The bigger the climate variation, the bigger the distortions of the floorboard and thus the bigger the potential for squeaking. In addition, other disadvantages of solid-wood flooring systems with click systems is that the floorboards typically have visually unpleasing gaps after installation, can be difficult to install, and are limited to narrow widths.
It is known that hygroscopic distortions and the resulting squeaking can be reduced by the application of a layer of wax on the contacting surfaces of the interlocking joint system. The wax has two purposes. The first is to seal the surface of the interlocking joint system to create a moisture barrier to reduce shrinkage and/or expansion of the floorboards. The second is to create a layer with a low coefficient of friction on the contacting surfaces of the interlocking joint system in order to reduce friction and thus squeaking.
But such wax systems and methods have several disadvantages. One common problem is that the wax is difficult to apply so that it fully seals the contacting surfaces of the interlocking joint system, so the floorboard is still affected by climate change and subject to frictional squeaking. Typically, the wax is sprayed onto the contacting surfaces and then dried with heat. The wax material is spray-applied in the liquid state, so it tends to penetrate into the wood pores (grain), and this affects the quality and consistency of the seal.
The wax penetration and sufficiency of the sealing of the contacting surfaces depends on the wax-material quantity, quality, viscosity, and temperature, as well as the application climate (e.g., temperature and humidity) and the wood species and density. With respect to the wax quantity, if too little is used such that too much of the wax penetrates into the wood pores, the contacting surface will not be sufficiently covered (thickness and coverage area) and squeaking will still occur. To make sure the contacting surfaces are covered by wax with a sufficient thickness and coverage area, no matter the penetration rate, the quantity of wax applied can be increased, but this greatly increases the cost.
With respect to the wax quality, even the highest-quality wax can degrade over time. After a long period of use, for example a few years, the wax tends to become drier and harder. Sometimes, it will crack and peel off, thereby leaving the contacting surfaces unprotected. This will affect the ability of the wax to protect the floorboard against humidity, with the result that the floor might start squeaking. In addition, wax quality is affected by temperature and humidity, and so the wax quality changes from winter to summer. This is the reason why many wood flooring systems with click systems, even those with wax, squeak during only one season of the year and not during the other seasons.
And with respect to the wood species and density, even within the same species, wood characteristics can be very different. For example, white oak from Europe has rather wide annual growth-ring circles with big pores, while white oak from Russia has rather narrow annual growth-ring circles with smaller pores. These differences affect the wax penetration and resulting surface sealing.
The result is that these numerous parameters affecting the penetration of the wax make the seal quality inconsistent and unreliable. As a consequence, often the flooring will squeak, if not in most places, then at least at a few localized places.
It is also known that some conventional click systems include separate metal clips in connection with rubber parts in order to avoid contact between the wood surfaces. For example, such click systems can be provided by drop-lock systems (with or without separate locking elements 22) as shown in FIG. 4, snap-lock systems (with or without separate locking elements 24) as shown in FIG. 5, rotatable lock systems (with or without a separate locking element) (not shown), and other click systems with or without separate locking elements. Such click systems and methods have several disadvantages. One is that contact points between surfaces of adjacent wood floorboards remain, and so squeaking might still occur when those surfaces rub against each other. Another is that such systems and methods do not provide moisture protection, so the floorboard size and shape are distorted by humidity and temperature variations.
Accordingly, it can be seen that there exists a need for improvements in click-type interlocking joint systems for solid-wood flooring systems. In particular, there exists a need for solid-wood flooring with a click system providing for minimized/eliminated squeaking and wider floorboards all manufacturable by cost-effective production methods. It is to the provision of solutions to this and other problems that the present invention is primarily directed.